The old avast 4.8 had a blue icon, avast 5.x and avast 6.0 have an 'Orange' tray icon.
So what version do you have, 6.0.1000 is the latest version ?
If you have avast 5.x or 6.0 provided you have internet connection you can register through the avastUI (left click the avast tray icon), Maintenance, Registration.